Add close connection functionality to WebSocket client

[Copilot]

This PR adds a graceful close connection function to the BinaryOptionsTools-v2 WebSocket client, addressing the need for proper connection management.

Changes Made

Core WebSocket Client (crates/core/src/general/client.rs)

• Added shutdown_sender: Sender<()> field to WebSocketInnerClient for signaling shutdown
• Modified event loop to check for shutdown signals and send WebSocket close frames
• Added close() method that gracefully terminates the connection:

  pub async fn close(&self) -> BinaryOptionsResult<()>

PocketOption Client (crates/binary_options_tools/src/pocketoption/pocket_client.rs)

• Added public close() method that delegates to the underlying WebSocket client
• Comprehensive documentation with usage examples
• Basic test coverage to verify functionality

Usage

Users can now gracefully close connections:

let client = PocketOption::new("your-ssid").await?;
// ... perform trading operations ...
client.close().await?; // Gracefully close the connection

Implementation Details

• Graceful shutdown: Sends proper WebSocket close frame to remote peer
• Clean termination: Signals event loop to stop processing without abrupt disconnection
• Non-breaking: All existing functionality remains intact
• Thread-safe: Uses async channels for safe cross-task communication

The implementation follows the existing patterns in the codebase and maintains backward compatibility while adding the requested close connection capability.

Fixes #16.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• demo-api-eu.po.market
  • Triggering command: /home/REDACTED/work/BinaryOptionsTools-v2/BinaryOptionsTools-v2/target/debug/deps/binary_options_tools-bf0e6b2adb8abbb6 test_close_connection (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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[theshadow76]

Nothing changed